1. Field of the Invention
The present invention relates generally to a cord and its application, and more particularly to a ladder tape for a window covering and a slat adjusting apparatus of a window blind using the ladder tape.
2. Description of the Related Art
There are lots of ways to weave cords for various purposes of a ladder tape. FIG. 1 and FIG. 2 show a conventional ladder tape 1 for a window blind. The ladder tape 1 includes two parallel cords, each of which has a weft string 1a and two warp strings 1b, 1c. The weft string 1a winds around the warp strings 1b, 1c in a specific way. The weft string 1a forms several transverse coupling sections 1d to support slats 2 of the window blind (as shown in FIG. 1) and an unwound section 1e (as shown in FIG. 2). The unwound section 1e lets the warp string s 1b, 1c having an unbounded section that an opening 1f is formed between the warp strings 1b, 1c. 
As shown in FIG. 2, a pin 3 passes through a gap 1g between the unwound section 1e and the weft string 1b, and then passes through the opening 1f through a path L. The pin 3 has a neck 3a that will be arranged to be located between the warp strings 1b, 1c so that the warp strings 1b, 1c may hold the pin 3. Next, the pin 3 is inserted into a rotary drum 4. The rotary drum 4 has a plate 4a to cover and press the pin 3 thereunder so to fix the pin 3 with the rotary drum 4. The rotary drum 4 is rotated to move the ladder tape 1 and tilt the slats 2.
The conventional apparatus for controlling the slats 2 has the following drawbacks:
1. The ladder tape 1 are fastened to the rotary drum 4 using an additional pin 3 that is difficult to assemble and the ladder tape 1 may be disengaged with the rotary drum 4 easily if the pin 3 becomes loose within the rotary drum 4.
2. The pin 3 is inserted into the gap 1g between the unwound section 1e and the warp string 1b and the opening 1f that will have a risk of breaking the unwound section 1e. 
3. The unwound section 1e may be entangled with other objects unexpectedly because it is exposed without any protection.